HP32E Repairing

[ElectroDuende]

Hi guys,

A couple of days ago I got a really nice (at least externally) HP32e unit, made in Singapore in 1979. It didn't work; in fact, one of the battery tabs was broken, and there were signs of corrosion on the battery PCB.

I opened it in seconds, with almost no effort, using the technique described here:

http://www.voidware.com/calcs/spicerepair.htm

And this is what I found inside...









As you can see the leaked battery electrolyte has completely destroyed the flex cable from the batteries, and is already attacking the flex cable that links the power board and main board. I'll cut out the damaged part and replace it by a segment of flat cable taken from an old HDD bus.

Fortunately the LED display and power board are free of corrosion (that white spot on power board has not gone under the protective layer, and the blue spots on the leftmost LED are actually on the surface of the lens, out of the "danger zone"). Main flex PCB is also in very good shape:







Something that surprises me is that I've read in several threads of this forum that HP32E lacks the central small IC, and my unit has them all... any explanation for this?





There is one missing pin in that IC, but it seems to be normal in other members of Spice series...

I hope I can come back here tomorrow with good news!

[ElectroDuende]

(10-11-2015 11:03 PM)ElectroDuende Wrote:  Hi guys,

A couple of days ago I got a really nice (at least externally) HP32e unit, made in Singapore in 1979. It didn't work; in fact, one of the battery tabs was broken, and there were signs of corrosion on the battery PCB.

I opened it in seconds, with almost no effort, using the technique described here:

http://www.voidware.com/calcs/spicerepair.htm

And this is what I found inside...

[...]

As you can see the leaked battery electrolyte has completely destroyed the flex cable from the batteries, and is already attacking the flex cable that links the power board and main board. I'll cut out the damaged part and replace it by a segment of flat cable taken from an old HDD bus.

Fortunately the LED display and power board are free of corrosion (that white spot on power board has not gone under the protective layer, and the blue spots on the leftmost LED are actually on the surface of the lens, out of the "danger zone"). Main flex PCB is also in very good shape:

[...]

Something that surprises me is that I've read in several threads of this forum that HP32E lacks the central small IC, and my unit has them all... any explanation for this?

[...]

There is one missing pin in that IC, but it seems to be normal in other members of Spice series...

I hope I can come back here tomorrow with good news!

Unfortunately the repair was not successful... or, at least, not completely.

It was quite easy to clean all the blue dirt from the battery PCB and to solder a flat cable from there to the power board... but I'm afraid that the LED display has a fault. And considering how it is driven, it is not a falt due to contacts but to the LED module itself.





As you can see, the top segment of second digit, and half of both segments close to it don't ligth. This makes it impossible to tell apart 1 and 7, rendering calculator mostly unusable.

I see that the LED substrate itself is glued to the base and soldered with thin wires... basically impossible to replace but with another complete display. I'll try to locate a donor, but I'm afraid that any calculator, bad enough to be a donor, will probably have a display in worse conditions... :-(

[Harald]

(10-12-2015 02:00 AM)ElectroDuende Wrote:  

(10-11-2015 11:03 PM)ElectroDuende Wrote:  Hi guys,

A couple of days ago I got a really nice (at least externally) HP32e unit, made in Singapore in 1979. It didn't work; in fact, one of the battery tabs was broken, and there were signs of corrosion on the battery PCB.

I opened it in seconds, with almost no effort, using the technique described here:

http://www.voidware.com/calcs/spicerepair.htm

And this is what I found inside...

[...]

As you can see the leaked battery electrolyte has completely destroyed the flex cable from the batteries, and is already attacking the flex cable that links the power board and main board. I'll cut out the damaged part and replace it by a segment of flat cable taken from an old HDD bus.

Fortunately the LED display and power board are free of corrosion (that white spot on power board has not gone under the protective layer, and the blue spots on the leftmost LED are actually on the surface of the lens, out of the "danger zone"). Main flex PCB is also in very good shape:

[...]

Something that surprises me is that I've read in several threads of this forum that HP32E lacks the central small IC, and my unit has them all... any explanation for this?

[...]

There is one missing pin in that IC, but it seems to be normal in other members of Spice series...

I hope I can come back here tomorrow with good news!

Unfortunately the repair was not successful... or, at least, not completely.

It was quite easy to clean all the blue dirt from the battery PCB and to solder a flat cable from there to the power board... but I'm afraid that the LED display has a fault. And considering how it is driven, it is not a falt due to contacts but to the LED module itself.





As you can see, the top segment of second digit, and half of both segments close to it don't ligth. This makes it impossible to tell apart 1 and 7, rendering calculator mostly unusable.

I see that the LED substrate itself is glued to the base and soldered with thin wires... basically impossible to replace but with another complete display. I'll try to locate a donor, but I'm afraid that any calculator, bad enough to be a donor, will probably have a display in worse conditions... :-(

Congratulations on getting this far! You'll just have to be patient and wait for a cheap Spice calculator on ebay, sometimes you can pic up physically damaged units with working LEDs relatively cheap.

Good Luck!
Harald

[jebem]

Hi!

Did you manage to progress on this display issue?

I'm planing to acquire my first Spice machine and considering the high prices asked for "untested" ad "sold as is" items, I'm afraid of getting one specimen with exactly the same issues.

As a side note, I found a picture of a "modified" HP-32E machine using 3 x AA battery cells for a total of 4.5Volt.

Cosmetically considerations aside, for a machine designed to operate with 2.5VDC at most, applying 4.5VDC is kind of power supply stressing, and I'm not sure about the LED operation.
Do you know if the LED module power lines are coming directly from th battery supply bypassing the regulated dc-dc power supply?

Here and here.

[ElectroDuende]

(11-10-2016 02:18 PM)jebem Wrote:  Hi!

Did you manage to progress on this display issue?

I'm planing to acquire my first Spice machine and considering the high prices asked for "untested" ad "sold as is" items, I'm afraid of getting one specimen with exactly the same issues.

As a side note, I found a picture of a "modified" HP-32E machine using 3 x AA battery cells for a total of 4.5Volt.

Cosmetically considerations aside, for a machine designed to operate with 2.5VDC at most, applying 4.5VDC is kind of power supply stressing, and I'm not sure about the LED operation.
Do you know if the LED module power lines are coming directly from th battery supply bypassing the regulated dc-dc power supply?

Here and here.

Hi Jose,

No, I'm afraid that all Spices that I had lately monitored on Ebay have finished too much expensive for me (even dfective models). I'll keep on waiting...

Regarding that mod, it is strange; the guy states "since the output voltage from the original rechargeable battery was 4.2-4.7 volta" but that is a bad asumption; as we all know here, they use 2x NiCd, that will be 2.4v (maybe he read about classic models and mixed things up).

And sorry, I have no idea if the power for the LED display comes from the DC-DC converter or directly from batteries... but I suppose it comes from the converter, as the brigth is quite constant during all battery life (although I use NiMH in my HP34C, and they have quite a flat discharge curve).

[jebem]

(11-13-2016 08:51 PM)ElectroDuende Wrote:  No, I'm afraid that all Spices that I had lately monitored on Ebay have finished too much expensive for me (even defective models). I'll keep on waiting...

[...]I have no idea if the power for the LED display comes from the DC-DC converter or directly from batteries... but I suppose it comes from the converter, as the bright is quite constant during all battery life (although I use NiMH in my HP34C, and they have quite a flat discharge curve).

Thanks for your reply.

Concerning the LED display, I was curious where it can be repaired.
Assuming the issue is a broken bond wire (as per Kees description), a new thin wire could be soldered to the pcb and then just bent to make contact with the led segment; a small drop of conductive paint would fix it.
Of course this would require a magnifying system.
You know that these led segments can be tested in the usual way with just a multi-meter set to diode testing (I tested my LED display in this way using a Protek 505 which presents 2.9V in open connection).

Meanwhile I found the answer for my LED display power supply question. As you said, it is regulated from the DC-DC converter (Kees has published power supply schematics here).

[ElectroDuende]

(11-14-2016 03:10 PM)jebem Wrote:  Concerning the LED display, I was curious where it can be repaired.
Assuming the issue is a broken bond wire (as per Kees description), a new thin wire could be soldered to the pcb and then just bent to make contact with the led segment; a small drop of conductive paint would fix it.
Of course this would require a magnifying system.
You know that these led segments can be tested in the usual way with just a multi-meter set to diode testing (I tested my LED display in this way using a Protek 505 which presents 2.9V in open connection).

I'm afraid that mine doesn't seem to be a broken wire. If you look at the detail picture, you will see that half of both vertical top segments ligth. This means that it is the led substrate itself what has been attacked by the corrosive spill of the batteries. Later I removed the plastic lens, and you can see that the base changed colour, and not to a good colour...

Atenciosamente